The dynamics of transportation, accumulation, diminishment and distribution of ⁹⁵Nb in a simulated aquatic ecosystem was studied using the isotope-tracer technique, and a fitting equation was established by application of a closed, five-compartment model. The results showed that when ⁹⁵Nb was introduced into an aquatic system, it was transported and transformed via deposition in combination with other ions, and adsorption and absorption by aquatic organisms, resulting in redistribution and accumulation in different parts of the organisms. Following addition, the spe- cific activity of ⁹⁵Nb in water decreased sharply within a short time, and then after reaching a certain value, it decreased more slowly. Sediment accumulated large amounts of ⁹⁵Nb through the exchange of ions. Hyacinth (Eichhornia crassipes) also adsorbed a large amount of ⁹⁵Nb in a short period of time. Snails (Bellamya purificata) and fish (Carassius auratus) were found to have a poor adsorption capacity of ⁹⁵Nb. The amount of ⁹⁵Nb found in the snail flesh was greater than that in the shell, and the ⁹⁵Nb found in the fish was mainly distributed in the viscera. The amount of ⁹⁵Nb in each individual component of the experimental system was affected over time.